Cocaine addiction remains a major public health problem in industrialized countries. However, up till now, efforts to find effective therapies for cocaine addiction have been unsuccessful. Recent studies of the dopamine transporter (DAT) have provided strong evidence of differential sites for dopamine translocation and cocaine binding. In view of this knowledge, the strategy of identifying pharmacological agents that block cocaine binding to the DAT but do not inhibit dopamine uptake as effectively as cocaine has emerged. We have proposed the hypothesisthat peptides, generated from the antigen-combining regions of anti-idiotypic (Ab2 beta) antibodies and selected for their ability to inhibit cocaine binding to the DAT without interfering with dopamine uptake, should function as therapeutic "cocaine antagonists." In this project, we will pursue four specific aims: 1. Characterization of Fab fragments of selected Ab 2beta with respect to their binding affinity and specificity for the DAT 2. Generation of scFv by cloning and expression of the antigen-combining regions of the selected Ab 2beta 3. Investigation of the ability of these scFv to block cocaine binding to the DAT without interfering with dopamine uptake 4. Sequence data analysis